At this stage, with all the available facts made public by now, I am almost inclined to see a very very sad problem here. The russian crew had all the equipment, and it also appears that this equipment worked as expected, and they simply failed to have the knowledge about this system.
Being in a position to listen and follow orders, they did as they use to do for as ling as they worked as an aircrew. The "intrusive" call of the TCAS created some confusion but was superseeded (in their views) by the ATC call to start decent!
It is not enough to have a little knowledge....